1. Field of the Invention
This invention relates to the treatment of subterranean, hydrocarbon-bearing formations. In one aspect, it relates to an improved well treatment method which employs resin-coated particulate material.
2. Description of the Prior Art
In the completion and operation of oil wells, gas wells, water wells, injection wells, and similar boreholes, it frequently is desirable to alter the producing characteristics of the formation by treating the well. Many such treatments involve the use of particulate material. For example, in hydraulic fracturing, particles (propping agent) are used to maintain the fracture in a propped condition. Also, in sand control techniques, particulate material is placed in the well to prevent the influx or incursion of formation sand or particles.
Particulate material in the form of silica sand and gravel have long been used in hydraulic fracturing treatments and gravel pack completions, and because of their low cost and availability remain the most common materials used in such operations. Recognizing the deficiencies of sand and gravel in certain types of treatments, the industry has recently introduced a variety of improved particulates. One such material is resin-coated particles disclosed in U.S. Pat. No. 3,929,191 issued in the name of John W. Graham et al. According to the method described in this patent, particles coated with a fusible thermosetting resin are placed in the well (either in the fracture or around the wellbore opposite the producing formation) and permitting to cure. The resin at formation temperature fuses (i.e. softens) and then cures to a solid infusible condition. The softening of the resin causes the coatings of contiguous particles to fuse together such that upon curing the particles are bonded together. This produces a strong, consolidated and permeable framework for conducting formation fluids.
Resin-coated particles have proven successful as proppants and as a gravel packing medium. One problem associated with this material however, is the temperature dependence of the resin compressive strength. Some resins do not cure at temperatures below 130.degree. F. or slowly at temperatures below 200.degree. F. This means that at low reservoir temperatures, resin-coated sand cannot be cured or excessive set time may be required to attain satisfactory compressive strength. In some well operations, long down times are expensive or undesirable from an operational point of view.